Commercial satellites, private space flight, and just about everything else that travels outside the atmosphere uses hydrazine as a propellant. It’s super toxic and dangerously unstable, so NASA is going to spend up to $50 million apiece to test alternatives.
One of the potential solutions is simple aluminum powder and water ice, or ALICE. The nice thing about ALICE is that it could be manufactured at bases on the moon or Mars. Rockets would only need to power up with enough fuel to get them to the base, where astronauts could make more fuel to get them back, saving a lot of weight for the outbound trip.
NASA wants green rocket fuel, Network World.